1. Field of the Invention
This invention relates to a needle bar transfer device for a multi-needle sewing machine.
2. Description of Prior Art
In a sewing machine having a plurality of needle bars suppported by a common needle bar supporting arm, when one of the needle bars is driven by the main driving shaft of the machine, other needle bars are held in predetermined inoperative positions. For instance, in a sewing machine disclosed in U.S. Pat. No. 4,473,018, needle bars not driven by the main driving shaft are held in inoperative positions by pins each urged by a spring into a V-shaped groove formed in upper end of the needle bar. Spring forces of a sufficient strength are required for holding the needle bars assuringly in the inoperative positions. However, when the spring forces are selected to be excessive, a heavy depressing force must be applied at the time of transferring a needle bar for disengaging the needle bar from the spring biased pin. Furthermore, yielding of the springs makes it impossible to hold the needle bars in their inoperative positions, rendering the sewing machine to be inoperative.
Applicants' prior U.S. Pat. No. 4,474,124, granted Oct. 2, 1984, discloses a multiple needle sewing machine which utilizes a common flexible plate having three pawl members adapted to resiliently engage grooves adjacent the tops of respective needle bars. A spring is provided for normally biasing the plate upwardly to locate the unused needle bar in an elevated noninterfering position. Once again the resilient force of the flexible member presents a drawback in engaging and disengaging the individual needle bars form the holding member.